Study On Potassium Storage Properties Of Calix[6]Quinone As A High Specific Capacity Organic Cathode Material

Potassium ion battery（PIB）as a candidate of the next generation energy storage system began to enter people’s field of vision.At present,in the cathode materials of secondary batteries,organic quinone compounds are considered to be very promising energy storage materials because of their advantages such as resource sustainability,high theoretical specific capacity and adjustable structure.However,quinone compounds dissolve easily in electrolyte during the cycle,which leads to poor cycle stability of the battery and limits the development of quinone compounds in the batteries.In this paper,calix[6]quinone（C6Q）is used as the cathode material for PIBs,and potassium storage performance of C6Q in 0.8 M KPF₆/(propylene carbonate（PC）,ethylene carbonate（EC）-PC（1:1=v/v）and EC-diethyl carbonate（DEC）（1:1=v/v）is studied,but the electrochemical properties in this electrolyte is not satisfying.In order to furtherly improve the electrochemical performance of C6Q,the electrochemical properties of C6Q in1 M Potassium bis（fluorosulfonyl）amide（KFSI）/(PC,EC-PC（1:1=v/v）and EC-DEC（1:1=v/v）is studied.Although the electrochemical properties of C6Q is improved,C6Q is easily soluble in the electrolyte.It is not conducive to the cycle stability of the battery.Therefore,this paper uses the ultrasonic infusion method to encapsulate C6Q into the pores of ordered mesoporous carbon（CMK-3）,the C6Q/CMK-3 composite material is prepared to avoid direct contact between C6Q and the electrolyte.The cycle performance and rate property of the PIBs have been improved greatly.（1）C6Q is used as cathode material for PIBs,when 0.8 M KPF₆/（PC,EC-PC and EC-DEC）are used as the electrolytes,at a current density of 0.2 C,the initial discharge capacities of PIBs are 291 m Ah g^-1,308 m Ah g^-1 and 267 m Ah g^-1,respectively.After 100cycles,the capacities decays to 69 m Ah g^-1,65 m Ah g^-1 and 51 m Ah g^-1,respectively.Their capacities are relatively low.When 1 M KFSI/（PC,EC-PC and EC-DEC）are used as the electrolytes,the initial capacities are 376 m Ah g^-1,412 m Ah g^-1 and 411 m Ah g^-1,respectively,indicating that the 12 carbonyl active sites of C6Q can be fully utilized and the capacities after 100 cycles are 131 m Ah g^-1,127 m Ah g^-1 and 117 m Ah g^-1,respectively.（2）C6Q/CMK-3 composite material is used as cathode,and 1 M KFSI/EC-PC is used as electrolyte for PIBs.At 0.2 C,the first discharge capacity can reach 442 m Ah g^-1,and there remain a capacity of 194 m Ah g^-1 after 100 cycles with a capacity retention rate of44%,53%higher than C6Q,the cycle performance has been greatly improved.In addition,the rate performance of C6Q/CMK-3 has also been enhanced.Even at high current of 5 C,the capacity is still 136 m Ah g^-1,which is a 31%improvement over the C6Q.